Was he perhaps planning to come back and install a short piece of outside corner molding there to pull it all together? I've seen that done by many installers though it's not my first preference.

Get him back to do this properly

Installation of cabinets is an area where the installer often has a lot of discretion, as there are such a large universe of individual conditions and solutions that there is no one standard procedure. Having said all of that, this detail isn't something I would allow on a high-end custom kitchen - but I might accept on a budget-driven job. If you bought your cabinets from Home Depot or Lowes, you are probably fighting an uphill battle. If you purchased through a builder, an interior designer, or an independent kitchen dealer, then I would expect better.

Yes, this is Lowes. But I'm holding out hope that he will come back and make it right when he comes back to do the three other things left unfinished. Thanks for the advice!

Call lowes n complain, n don't make any payments until its fixed.

I have found with great success that if you speak directly to the store manager of Lowes you will get good results. By that I mean show up in person with photo's and all paperwork.

The trim pieces might have come in that length? Did your cabinets fit flush against the wall? You probably will have to order another piece so he can lengthen all of them. Have the piece there when he comes back. He might have some trim left over?